Upgrade to servlet 3.0 and jetty 8

This patch upgrades spark to Servlet 3.0 and (latest) Jetty 8.

Issue: 43
Upgrade to servlet 3.0, jetty 9, and java 7

This patch upgrades spark to Servlet 3.0 and Jetty 9, and Java 7.

Issue: 43
Removed inherited from maven plugins

Inherited is true by default, so no point in setting it explicitly.

Issue: 43
Removed log4j from comment in pom

Removed log4j from comment since it's not being used as dependency.

Issue: 43
Added jetty dependencies section comment in pom

For consistency and readability, jetty dependencies section is marked
with a comment.

Issue: 43